1. Field of the Invention
The present invention relates to an improved process for the co-production of propylene oxide and styrene monomer and especially to improved recovery of valuable 1-phenyl ethanol and styrene from heavy residual process streams by acid treatment and cracking.
2. Description of the Prior Art
An extremely successful process for the co-production of propylene oxide and styrene monomer involves the molecular oxygen oxidation of ethyl benzene to form ethyl benzene hydroperoxide, the catalytic reaction of the hydroperoxide with propylene to form propylene oxide and 1-phenyl ethanol, and the dehydration of the 1-phenyl ethanol to styrene monomer. The basic patent describing this process is U.S. Pat. No. 3,351,635.
In practice of the process, various distillation steps are employed in order to separate unreacted reagents as well as various product streams, and generally one or more caustic treatment steps are employed in order to reduce the acidic characteristics of various streams.
In commercial practice of the propylene oxide-styrene monomer process there is formed a heavy residue stream containing, as a result of one or more caustic treatments, relatively high levels of sodium compounds. Heretofore, such heavy residue has comprised a low value product stream suitable only for use as a low grade fuel.